This invention relates generally to the art of rice shelling machinery and more particularly to the art of rice shelling machinery employing mating rollers.
The rice milling process, which removes the hull and other portions of bran and germ to yield the endosperm, involves various abrasive and separatory procedures. Attention is directed to the specific procedure for removing the hull or husk from the remaining kernel, i.e., the shelling procedure. The shelling procedure follows cleaning the paddy or rough rice and loosens the coarse husk from the kernel by either disk or rubber roll shellers. In recent times, the more efficient rubber roll sheller has been increasingly used, replacing the disk sheller in the marketplace since it provides a greater yield of hulled and undamaged kernels.
Rubber-surfaced rolls are positioned in parallel at a specific gap and rotate towards each other as rough rice is fed between them. This action results in a gentle removal of the husk which leaves the endosperm primarily intact, a prerequisite stage to further refinement of the kernel. Use of the currently employed rubber-surfaced rolls, however, has severe drawbacks due to both production and maintenance considerations. The roll consists of a hollow steel hub with a rubber surface. In order to manufacture the roll, the ductile steel herb must be sand-cast. The hub is then shaped by machine to produce both inside and outside finished dimensions. The rubber surface of the roll must be bonded to the steel hub in order to secure it in position. This procedure includes coating the hub with the bonding agent and loading it into a compression or transfer mold. Once bonded, machine shaping is required again to bring the rubber surface coaxial with the hub. Finally, all exposed metal surfaces of the hub require painting in order to prevent rusting. The procedure is time consuming and involved, and is currently being performed outside the country.
Furthermore, the life expectancy of the finished product averages only 2.6 days. But, since the process of refurbishing used rolls is extremely costly, inherently problematic and results in a product of lesser quality than a new one, new rolls are supplied when needed. Production time and intricacy combine with freight costs and shipping time to present major obstacles to the employment of the roll used currently in rice shelling machinery.
Specialized machines have existed within the prior art which address various separatory procedures. U.S. Pat. No. 4,393,762 to Jacobs discloses a machine for dehulling flat disc-like seeds whereby a spinning rotor throws the seeds against an annular impact band to crack the hull. In U.S. Pat. No. 4,459,903 to Yamamoto, an abrasive roll rice polishing machine is disclosed. But, a need exists within the rice milling process for improving the rice shelling procedure, particularly by addressing machines employing mating rollers.